Barium calcium magnesium stearate grease



Patented e0, 1945 2,389,523 BARIUM CALCIUM MAGNESIUM STEABA'IE GREASE Frank A. Leyda, Berkeley, Calif., .assirnor, by

mesne assignments, to California Research Ourporation, San Francisco, (Built, a corporation Delaware No Drawing. Application November 2, 1943,

Serial No. 508,749 1 8 Claims.

This invention relates to the preparation of lubricating greases and the greases produced thereby. particularly one which is waterproof,

- high melting and thermally reversible.

The three most commonly used bases for creases are social, lime and aluminum soaps. Each type ol grease made from these bases has oertalc advantages as well as disadvantages. emu base rrreases have high melting points and are thermally reversible; 1. e., on melting and then cooling to solidify, a soda base grease reverts to its original state. It does not break into an oil phase and a soap phase upon melting. However, due to the water solubility of the soda soaps, greases made from this material as a base lack waterprootqualities and will tend to emulsiiy with any moisture that may be present.

Lime or calcium base greases are waterproof, but melt at relatively low temperatures, about roar F. Under these conditions they lose the water which is a minor but essential component or this type of grease and break into an oil phase and a soap phase. Thus, in addition to being low melting, which in itself is undesirable, lime base greases are not thermally reversible.

Aluminum base greases are waterproof but term a rubbery gel at about 200 F. also, althoulgh aluminum base greases have an apparent melting point by the Ubbelohde or bulb methods as high as 250 to 1-390 it will be found that they will soiten suficiently to flow at temperatures oi.

about Bill)" F. This may be demonstrated by placins a small sample of the grease upon a S-mesh metal screen and heating it for several hours. Since many service conditions will impose a temperature of over 200 F. for prolonged periods,

it is apparent that aluminum base greases are not high melting in the sense that soda base greases are highmelting.

By way of improvement, it has been heretofore proposed to use barium base or mixed bariumcalcium base greases in lieu of straight calcium base greases. Such greases have certain advantages, due chiefly to the barium base. Barium soaps, for example barium stearate, have the property of imparting to a grease a higher meltin: point than calcium soaps. At the same time the barium base grease retains the waterproof qualities of the calcium base material. Examples of these are described in United States Patents Nos. 2,033,149 and 2,154,383 to Thomas F. on et a].

' chiefly, such barium base creases include basic barium soap or a mixture ol normal and basic barium soaps with petroleum oils or varying viscosity characteristics. Grease wherein the soap base is largely or entirely normal barium soap have a lower melting point than those in which the soap is of the basicvariety. Mined bariumcalcium base greases are described in United States Patent No. 213N381 to L. U. Brunstrum et 9.1. These are said to be Superior not only to the lime or calcium base creases but also to the straight barium; base creases, in that they will not stiilen upon heating above 250 F. The mixed barium-calcium base greases are preferably used in conjunction with a partial ester of a polyhydrlc alcohol and a higher fatty acid, such as diglycol stearate. The combined eflect oi the mixed barium-calcium base and the partial ester is much greater than the enact oi thebarlumcalcium base alone. This is particularly true of the anhydrous greases.

It is an object or the present invention to produce a grease having certain characteristics, cl calcium base greases and which combines several advantages and lacks several disadvantages of heretofore lmown greases.

It is alurther and particular object or this invention to produce a grease which has a high melting point, is waterproof, and is thermally rcversible and which is free from the objectionable lectures or heretofore known substitutes for cal cium base greases.

Another object is to provide a method oi pro= ducing an anhydrous grease which will be thermally reversible and will have improved resistance against melting at high temperatures.

These and other objects or this invention will be further apparent from the following descrlption of a preferred embodiment together with selleral alternative compositions.

part or in whole for the calcium in the base material.

In compounding greases according to the invention, the oil component will be selected and used from those petroleum oils which have hitherto been used in grease making. In a typical example, commercial stearlc acid (a mixture of stearic and palmitic acids), barium hydroxide octahydrate, hydrated lime, magnesia and a mineral lubricating oil in quantity suilicient to render the mixture and the reaction produce freely fluid at an elevated temperature are stirred and heated in an autoclave at about 300 to 330 F. until saponification and intermixture are complete. After releasing the pressure, thereby flashing of! a portion of .the water, the autoclave is opened and the mixture heated further until substantially all of the water is driven off, after which sufllcient mineral oil is.added and stirred in to produce a grease of the desired consistency or hardness. After the mineral oil is added the grease is stirred and cooled to about 150 F. before drawing from the autoclave. It will be understood, however, that other procedures of compounding may be employed so long as the base comprises soaps of barium, calcium and magnesium and the saponifled mixture is heated until substantially all the water is driven oil to form an anhydrous product.

The term stearic acid is used in this description to designate both the comparatively pure acid and also the commercial product which may contain a substantial fraction, in some cases up to 40%, of palmitic acid.

The barium soap is preferably employed in greater amount than either of the other soaps and it is most advantageously used in an amount by weight exceeding the combined magnesium and calcium soaps. The preferred proportions of the various soaps are set forth in the table below: I 7

Per cent by weight of total soap Barium soap 60 to 80 Calcium and/or strontium soap 10 to 30 Magnesium soap 10 to 20 As stated above, strontium may replace a part or all of the calcium soap, andv the stearic acid radicalmay be replaced in part or entirely by the palmitic acid'radical. Furthermore, other fatty acids may be used, such as the material sold under the trade-mark Hydrex" derived from hydrogenated fish oil or similar oils and which consists of a mixture of saturated fatty acids in which the number of carbon atoms varies from about 14 to 22 or more. A typical average distribution would be as follows:

Per cent C-14 7 0-16 32 0-18 23 C-20 23 C22+ 15 cordance with this invention possesses a remarkable number of desirable properties. It is waterproof. like the-calcium and aluminum base greases, but unlike both the latter it has a high melting point. Unlike aluminum base greases it does not gel to a rubbery state on heating. 0n the contrary, as it is heated to above the melting point it changes from a solid to a viscous liquid, and on cooling it again assumes the same solidform. Even repeated melting and solidification do not cause the oil and soap to separate, so that it is truly thermally reversible Neither water nor any other substance besides the soaps and the oils is essential to its manufacture. Preferably, it is employed in an anhydrous form although a very small percentage of water may be present as is the case of substantially any form of grease.

Following are specific compositions of greases which have been found to be very desirable in their properties:

Composition Example 1 Example 2 lercml I'm'mt Btoarlc acid, percent by weight 17.86 10.50 iiydrutod barium hydroxide. 7. A2 0.05 liydru cd limo 0. 47 0.14 Magnesia 0.3) 0.15 Acid treated naphthcnlc base mineral oil of viscosity 460 H. H. U. at 100 F 7T1. it'i flnivcnt trcntcd rm )htlu'nic haso mincrnl oil of vlscos ty 360 S. H. U. at

A. S. 'I. M. penetration, 77 F.:

Unworkcd 125 158 Worked 215 242 Mcitlng point, "F 205 250 In conclusion, it will be appreciated that the essential features of this invention appear to reside in the manufacture of an anhydrous grease which is waterproof, thermally reversible and of a high melting point, made from a mixture of barium, magnesium and calcium or strontium soaps with a mineral oil. Although specific examples of compositions, methods of compounding and the like have been given, it will be appreciated that modifications may be made which will not depart from this invention so that all such modifications and changes as fall within the scope'of the appended claims will be embraced thereby.

1. A mixed base, anhydrous grease consisting of mineral oil and soaps of barium, magnesium I and at least one metal of the group consisting of calcium and strontium, said magnesium soap being present in proportions ranging from 10 to 20% of the soaps present so as to produce a thermally reversible grease.

2. A mixed-base, anhydrous grease consisting of mineral oil and stearates and palmitates of barium, calcium and magnesium, said magnesium stearates and palmitates being present in such proportions as to produce a thermally reversible grease.

3. A mixed-base, thermally reversible grease consisting of mineral oil and a soap mixture, said soap mixture comprising about 10 to 20% by weight of magnesium stearate, the other soaps comprising calcium and barium stearates, the barium stearate exceeding the combined calcium and magnesium stearate content.

4. A mixed base, anhydrous, thermally reversible grease comprising mineral oil and a soap mixture, said soap mixture composed of 60 to 80% barium soap, to calcium soap and 10 to 20% magnesium soap.

5. A mixed base, anhydrous, thermally reversible grease comprising mineral oil and a soap mixture, said soap mixture composed of to 80% barium soap, 10 to 30% strontium soap and 10 to 20% magnesium soap. 1

6. A mixed base, anhydrous, thermally reversible grease having approximately the following percentage composition by weight:

Per cent Barium soap 18 Calcium soap 4 Magnesium soap 3 Oil "7. A mixed base, anhydrous, thermally revers ible grease having approximately the followin percentage composition by weight:

Barium soap Strontium so p Magnesium soap Oil 8. A mixed-base, anhydrous thermally reversible grease comprising mineral oil and a soap mixture, said soap mixture composedof 60 to barium soap, 10 to 20% magnesium soap, and about 10 to 30% of soap chosen from the group consisting of calcium and strontium soaps.

' A. LEYDA. 

